linux-kernel - Re: [Patch Part2 V1 11/14] iommu/vt-d, PCI: update DRHD/RMRR/ATSR device scope caches when PCI hotplug happens

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Date:	Thu, 9 Jan 2014 16:52:01 +0800
From:	Yijing Wang <wangyijing@...wei.com>
To:	Jiang Liu <jiang.liu@...ux.intel.com>,
	Joerg Roedel <joro@...tes.org>,
	David Woodhouse <dwmw2@...radead.org>,
	Yinghai Lu <yinghai@...nel.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Dan Williams <dan.j.williams@...el.com>,
	Vinod Koul <vinod.koul@...el.com>
CC:	Ashok Raj <ashok.raj@...el.com>, Tony Luck <tony.luck@...el.com>,
	<iommu@...ts.linux-foundation.org>, <linux-pci@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <dmaengine@...r.kernel.org>
Subject: Re: [Patch Part2 V1 11/14] iommu/vt-d, PCI: update DRHD/RMRR/ATSR
 device scope caches when PCI hotplug happens

Hi Gerry,
   This is patch solution is better than mine, it's more reliable.
I tested this patch in my huawei RH5885 platform, after applied it,
the issue is gone. But I can not test it in the case that bus number changed
after hotplug. Anyway, it's a good solution.

Thanks!
Yijing.

On 2014/1/7 17:00, Jiang Liu wrote:
> Current Intel DMAR/IOMMU driver assumes that all PCI devices associated
> with DMAR/RMRR/ATSR device scope arrays are created at boot time and
> won't change at runtime, so it caches pointers of associated PCI device
> object. That assumption may be wrong now due to:
> 1) introduction of PCI host bridge hotplug
> 2) PCI device hotplug through sysfs interfaces.
> 

> diff --git a/drivers/iommu/dmar.c b/drivers/iommu/dmar.c
> index 31c72d5..15c9ce0 100644
> --- a/drivers/iommu/dmar.c
> +++ b/drivers/iommu/dmar.c
> @@ -194,6 +194,209 @@ void dmar_free_dev_scope(struct pci_dev __rcu ***devices, int *cnt)
>  	*cnt = 0;
>  }
>  
> +/* Optimize out kzalloc()/kfree() for normal cases */
> +static char dmar_pci_notify_info_buf[64];

In my idea, pci device add/remove is not a frequent action, so maybe using kzalloc and kfree make
code more simplified, this is just my personal opinion.

> +
> +static struct dmar_pci_notify_info *
> +dmar_alloc_pci_notify_info(struct pci_dev *dev, unsigned long event)
> +{
> +	int level = 0;
> +	size_t size;

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